1. Field of the Invention
This invention refers to a device for a flywheel magneto with an electronic ignition system in combination with a generator.
2. Prior Art
It is a known fact that flywheel magnetos having an electronic ignition system in combination with a generator and a trigger release of the ignition pulse are, for the exact ignition function, extremely dependent on the magnetic field which causes the trigger pulse being as far as possible uninfluenced by the other magnetic fields in the system. With regard to the total output of the magneto, these fields must as a rule be made very strong, with the result that leakage fields can occur which influence the separately arranged magnetic field for the trigger coil. Since the load on the generator side varies as the power take-off from zero to maximum, the magnetic flux which creates the generator current will also vary considerably. It is these flux alterations which can, in combination with a varying speed for the flywheel magneto, adversely affect the trigger function to cause displacements in the spark position, among other things.
The only technical cure available with flywheel magnetos of the kind discussed is to provide an as effective magnetic screen as possible between the often strong magnetic fields of the generator part, and the relatively considerably weaker magnetic field or fields causing the trigger pulse. In another embodiment, the generator with associated permanent magnets is arranged inside the flywheel, in tandem with an armature having permanent magnets, mounted above the flywheel. The charging coil required for the ignition function, together with the trigger coil is arranged in connection with the armature. In this arrangement the flywheel, which is intended to be of ferromagnetic material, forms a screen between both the magnetic fields, extremely effectively preventing any mutual influence. The ignition side is completely separated from the generator side in that the armature mounted above the flywheel causes both the magnetic field required for the charging coil and the magnetic field which causes the trigger pulse.
In another embodiment, in order to reduce the total installation height of the magneto apparatus as much as possible, the trigger coil is arranged, possibly with accompanying electronic components, under the flywheel instead of above it. In such a case a special trigger magnet must be mounted on the inside of the wheel for coaction with the trigger coil. The trigger magnet is then placed on the inside of the cylindrical circumference of the flywheel, and will unavoidably lie side by side with the wreath of permanent magnets causing the rotating field for the generator part. In such arrangement, the trigger magnet lies very close to the permanent magnets of the generator side, and measures must unavoidably be taken to prevent flux influence between both magnetic systems.